Rubella (German Measles)
The rubella virus, a togavirus of the genus Rubivirus, is an enveloped single-stranded RNA virus with a single serotype that does not cross-react with other togaviruses. Humans are the only known host, with seasonal epidemics occurring every 5-9 years over a worldwide distribution. Rubella virus is transmitted by the respiratory route and the virus replicates in the nose, throat and the local lymph nodes. The incubation period ranges from 12 to 23 days, with an average of 18 days. Viraemia occurs 5-7 days after exposure and leads to viral spread to different organs.
In pregnant women the virus infects the placenta and the developing fetus. Infection by rubella virus is characterized by a transient rash. Joint pain and arthritis rarely occur in children, but may affect up to 70% of adults. Rubella virus can be found in nose and throat secretions and urine from 1 week before to 2 weeks after rash onset, although infants with congenital rubella may excrete the virus for a year or more in pharyngeal secretions and urine.
Congenital rubella syndrome is caused by infection in early pregnancy; from just before conception and during the first 8-10 weeks of gestation rubella infection may result in multiple fetal defects in up to 90% of cases, affecting many organs and often results in miscarriage or stillbirth. Infants with congenital rubella syndrome that survive may face serous developmental disabilities.
A number of vaccines are available either as single component or combined with either measles vaccine (MR) or measles and mumps vaccines (MMR). Most of the currently licensed vaccines are based on the live, attenuated RA 27/3 strain of rubella virus propagated in human diploid cells. Other attenuated rubella vaccine strains include the Matsuba, DCRB19, Takahashi, Matsuura and TO-336 strains used primarily in Japan, and the BRD-2 strain used primarily in China. Vaccination results in high (>95%) seroconversion rates and protection is generally assumed to be lifelong, although rubella antibodies may fall below detectable levels. Vaccine-induced immunity is generally assumed to be lifelong, although rubella antibodies may fall below detectable levels.
Rubella vaccine standardization
Requirements for rubella vaccines were first adopted in 1977 and amended in 1980. As rubella vaccines are routinely used in multi-antigen combinations with measles and mumps vaccines, WHO updated guidance for the three vaccines in 1992 into a single document which contains the requirements for the three monovalent vaccines and MMR.. In TRS 848 an amendment addressing the safety of the mumps antigen produced with a medium that contains serum was published.
Requirements for Measles, mumps and rubella vaccines and combined vaccines, live, TRS No. 840, Annex 3
A WHO reference material for live attenuated rubella vaccine is available to qualified applicants:
IABS Scientific Workshop on Neurovirulence Tests for Live Virus Vaccines, WHO, Geneva, Switzerland, 31 January-1 February 2005
Prequalified rubella vaccines
Rubella, and rubella containing vaccines (MR and MMR) are prequalified for procurement by UN organizations: